Solenoid-operated valve devices are in common use in numerous mechanisms and systems today. In particular, solenoid-operated valve devices are used in vehicle pressure regulators and the like.
The present invention is an improvement in solenoid-operated valve devices generally and more particularly relative to solenoid valve pressure regulators of the kind typically shown in U.S. Pat. No. 4,905,545. Regulators of the type disclosed in the '545 patent are adapted for use in a pressure control system for pressure-operated clutches and brakes of an automatic transmission in a vehicle driveline that includes an internal combustion engine with a throttle control.
A solenoid-operated pressure regulator of this type is also shown in U.S. Pat. No. 5,157,608 where the pressure regulator is used to establish a so-called throttle pressure, the magnitude of which depends upon the throttle setting of a throttle-controlled internal combustion engine.
It is desirable in an automatic transmission control system of this kind to regulate the clutch and brake apply pressure so that clutch or brake engagement is dependent upon the torque requirements that are required for a particular operating condition. As the engine throttle setting increases, the demand for torque increases, thereby making it necessary to increase the torque transmitting capacity of the clutch and brake friction elements.
The transmission system includes an enginedriven pump. In the case of the transmission system of the '545 patent, the outlet side of the pump supplies line pressure to a solenoid valve assembly that comprises a ball valve element situated in a pressure distribution passage, the outlet side of which communicates with a friction clutch or brake. A solenoid actuator, under the control of an electronic microprocessor, establishes an electromagnetic force on a solenoid armature which in turn triggers the operation of the ball valve element as a valve plunger engages and unseats the ball valve element.
The '545 patent describes both a normally vented solenoid valve assembly and a normally applied solenoid valve assembly. When the electromagnetic windings of the normally vented solenoid valve assembly of the '545 patent are de-energized, pressure in the supply pressure passage causes the ball valve element to seat against a valve seat that interrupts pressure distribution to the friction element. Simultaneously, a secondary valve element on the valve plunger becomes unseated as a flow passage is established between the pressure chamber for the friction element and the low pressure exhaust region of the circuit. When the solenoid is energized, the armature is moved, thus moving the plunger and the ball valve element and causing the ball valve element to become unseated from its valve seat. This permits pressure distribution from the line pressure passage to the friction element. Continued movement of the armature will cause the secondary valve element to become seated, thereby interrupting communication between the friction element and the vent.
In the system described in the '545 patent, the solenoid valve is a pulse-width modulated valve. During the portion of the cycle time for the solenoid in which the solenoid is energized, the secondary valve element moves toward its valve seat causing interruption of communication between the friction element and the vent as the ball valve element admits pressure from the supply pressure passage to the friction element. During the off time of the cycle, pressurized fluid flow from the supply pressure passage to the friction element is interrupted as the ball valve element seats on its valve seat which seals the supply pressure passage from the friction element. Simultaneously, the secondary valve element is unseated, thereby opening the friction element to the vent.
The rapid seating and unseating of the secondary valve element that occurs by reason of the cycling of the solenoid causes an undesirable valve vibration and noise. In the case of the normally applied solenoid valve assembly described in the '545 patent, the valve vibration and noise occurs as the ball valve element is seated and unseated.
The '545 patent describes one design attempt to alleviate this noise problem in a normally applied version of the solenoid valve assembly by providing a spring plunger that is engaged by the movable ball element as the solenoid is energized during the "on" portion of the cycle. The spring plunger acts as a damper as the movement of the ball valve element to its closed position is cushioned. During the "off" portion of the cycle, the spring of the spring plunger shifts the spring plunger into engagement with the ball valve element, causing the ball valve element to become unseated. As the ball valve element becomes unseated, flow once again is permitted to pass from the supply pressure passage to the friction element. This action is repeated as the solenoid windings are energized at a cycle frequency of approximately 50 pulses per second.
The device disclosed in U.S. Pat. No. 5,157,608 is a solenoid-operated ball valve arrangement that is used to establish a so-called throttle pressure in a control valve system of an automatic transmission. The solenoid valve assembly includes an armature that is spring loaded to cause a ball valve element to sealingly engage a port for supply pressure. When the solenoid windings of the actuator of the '608 patent are energized, the armature moves away from the ball valve element, thereby permitting the ball valve element to seat. This interrupts communication between the throttle pressure port and the exhaust port while increasing communication between the supply port and the throttle pressure port. By modulating the pulses for the solenoid windings, the effective pressure made available to the throttle pressure port can be controlled. No provision is made in the design of the '608 patent for preventing vibration and noise caused by the impacting of the ball valve element on its valve seat.
The cushioning arrangement described in the '545 patent involves a complex spring-loaded plunger and valve assembly that introduces manufacturing costs and complexity in the assembly procedure. It also requires careful calibration. An undesirable delay in the operation of the valve caused by the spring plunger adversely affects valve response time since the spring damping force is applied to the ball valve element before the ball valve seats in its valve seat during the "on" position of the solenoid energizing voltage cycle. Further, the cushioning arrangement includes moving valve parts that are sensitive to the presence of contaminants and changes in oil temperature.